Not Applicable
This invention relates to an ink jet printhead chip. More particularly, this invention relates to an inkjet printhead chip that includes a motion conversion mechanism.
As set out in the above referenced applications/patents, the Applicant has spent a substantial amount of time and effort in developing printheads that incorporate micro electro-mechanical system (MEMS)xe2x80x94based components to achieve the ejection of ink necessary for printing.
As a result of the Applicant""s research and development, the Applicant has been able to develop printheads having one or more printhead chips that together incorporate up to 84000 nozzle arrangements. The Applicant has also developed suitable processor technology that is capable of controlling operation of such printheads. In particular, the processor technology and the printheads are capable of cooperating to generate resolutions of 1600 dpi and higher in some cases. Examples of suitable processor technology are provided in the above referenced patent applications/patents.
Common to most of the printhead chips that the Applicant has developed is a component that moves with respect to a substrate to eject ink from a nozzle chamber. This component can be in the form of an ink-ejecting member that is displaceable in a nozzle chamber to eject the ink from the nozzle chamber.
As is also clear from the above applications, Applicant has developed a number of ways in which to achieve the ejection of ink from the respective nozzle chambers. A majority of these are based on the selection of a material having a coefficient of thermal expansion that is such that, on a MEMS scale, expansion upon heating and subsequent contraction upon cooling can be harnessed to perform work. The material is formed to define at least part of a thermal actuator that includes a heating circuit. The heating circuit is shaped to be resistively heated when a current passes through the circuit. The current is supplied to the circuit in the form of pulses at a frequency that depends on the printing requirements. The pulses are usually supplied from a CMOS layer positioned on a substrate of the printhead chip. The pulses are shaped and have a magnitude that is also dependent on the printing requirements. The generation and control of the pulses is by way of a suitable microprocessor of the type described in the above referenced applications.
On a macroscopic scale, it is counter-intuitive to use the expansion and subsequent contraction of material in order to achieve the performance of work. Applicant submits that the perceived slow rate of expansion and contraction would lead a person of ordinary skill in the field of macroscopic engineering to seek alternative energy sources.
On a MEMS scale, however, Applicant has found that expansion and contraction of such a material can be harnessed to perform work. The reason for this is that, on this scale, expansion and contraction are relatively rapid and can transmit relatively high force.
There remains an issue of range of movement. While the expansion and contraction are both rapid and forceful, Applicant has found that it would be desirable for a mechanism to be provided whereby such rapidity and force of movement could be amplified at a region where the work is required to eject the ink.
A majority of the nozzle arrangements covered by the above applications and patents use differential expansion in the thermal actuator to achieve bending of the thermal actuator. This bending movement is transmitted to an ink-ejecting component that is either rectilinearly or angularly displaced to eject the ink.
Applicant has found that it would be desirable for simple rectilinear expansion of a thermal actuator to be transmitted to an ink-ejecting component, since such simple rectilinear expansion on a MEMS scale is relatively efficient.
The Applicant has conceived this invention in order to achieve the desired transmission and amplification of motion mentioned above.
According to the invention, there is provided a printhead chip for an inkjet printhead, the printhead chip comprising
a substrate; and
a plurality of nozzle arrangements that is positioned on the substrate, each nozzle arrangement comprising
nozzle chamber walls and a roof that define a nozzle chamber with the roof defining an ink ejection port that is in fluid communication with the nozzle chamber;
an actuator that is displaceable, in a substantially rectilinear manner, with respect to the substrate;
an ink-ejecting mechanism that is angularly displaceable with respect to the substrate to eject ink from the ink ejection port; and
a translation to rotation conversion mechanism interposed between the actuator and the ink-ejecting mechanism to convert rectilinear movement of the actuator into angular displacement of the ink-ejecting mechanism.
The ink-ejecting mechanism may include an ink ejection member that is positioned in the nozzle chamber and is angularly displaceable with respect to the substrate to eject ink from the ink ejection port.
The actuator may have a fixed portion that is fixed to the substrate and a working portion that is capable of thermal expansion when heated to be displaced in said substantially rectilinear manner.
The translation to rotation conversion mechanism may include a pivot member that is pivotal with respect to the substrate. The pivot member may be connected to the working portion of the thermal actuator to pivot upon displacement of the working portion. The ink ejection member may be connected to the pivot member so that the ink ejection member is angularly displaced upon expansion of the working portion.
The nozzle chamber walls and the roof may be dimensioned so that the nozzle chamber is elongate and has a generally rectangular shape when viewed in plan. The nozzle chamber walls may thus include a distal end wall, a proximal end wall and a pair of opposed side walls, the pivot member being positioned adjacent the proximal end wall and the ink ejection port being positioned adjacent the distal end wall.
Each ink ejection member may be shaped to correspond generally with a plan profile of each nozzle chamber so that an end of the ink ejection member is positioned adjacent the ink ejection port.
Each pivot member and each ink ejection member may be configured so that the ink ejection member is between approximately 20 and 60 times longer than an effective lever arm defined by the pivot member. In particular, each ink ejection member may be approximately 40 times longer than the effective lever arm defined by the pivot member.
In a particular embodiment, the ink ejecting mechanism may be in the form of an active ink-ejecting structure. The active ink-ejecting structure may at least partially define the nozzle chamber and the roof that defines the ink ejection port that is in fluid communication with the nozzle chamber. The active ink-ejecting structure may be pivotally connected to the substrate. The actuator may be connected to the active ink-ejecting structure so that the active ink-ejecting structure is angularly displaced with respect to the substrate upon displacement of the actuator, to eject ink from the ink ejection port.
The printhead chip may be the product of an integrated circuit fabrication technique. The substrate may include a silicon wafer substrate and a CMOS layer positioned on the silicon wafer substrate, the CMOS layer being connected to the actuator of each nozzle arrangement to provide the actuator with electrical driving pulses.
The substrate may have a plurality of ink inlet channels defined therein, one inlet channel opening into each respective nozzle chamber.
The invention extends to an inkjet printhead that includes at least one printhead chip as described above.